1. Technical Field
The present invention relates generally to electrical conductors and insulators, and the apparatus specialized to mounting, protecting, encasing in conduits, and housing insulators, and more particularly to conduits and housings mounted on, in or through the walls of building structures.
2. Background Art
In most types of buildings today framing members, commonly called studs, are widely used in wall construction. Such studs are usually of wood or sheet metal, with the former typically used in residential buildings and the latter more common in commercial buildings. In a single family residence hundreds of studs may be used and in multi-family residences and commercial buildings thousands can be used. In most cases the studs are ultimately covered on both sides with wallboard, drywall, paneling, etc., thus enclosing them and the spaces between them within walls.
In stud-based construction it is usually necessary to run utility conduits through the studs before they are covered with wall surfacing. The nature of such conduits can vary widely, and herein is used generally to mean any means of conveying a utility. The earliest examples are conduits for plumbing used to convey fresh and waste water. Some more recent examples include pneumatic lines, used both to convey pressurized gasses and vacuum. Of course, in the last one-hundred years the most widely encountered example is electrical power wiring utility conduits (including, without limitation, bare wire [no longer widely used]; fabric and plastic clad wire by itself; and such encased in either flexible or rigid, metallic or non-metallic, pipe or cable sheathing). For instance, every room in residences, offices and stores today usually has multiple power receptacles, one or more lighting fixtures, and one or more switch stations for these. Also, of dramatically increasingly importance today, are utility conduits for communications. Modern homes and offices can employ low voltage electrical wiring for telephones, computer networks, door bells, speakers for intercoms and stereos, etc. Similarly, coaxial cable is widely used for television and video security, and even optical cable is now starting to be used widely.
For the sake of this discussion, the manner in which utility conduits are put into walls can be generally classified as either routing through through-notches in studs or routing through through-holes in studs. Through-notches are sections cut out of the edges of studs that will later be adjacent to a wall covering. This approach has been widely used in the past but is now largely out of favor because it is felt to unduly undermine stud and wall strength. Additionally, for reasons that will be discussed presently, this approach undesirably puts utility conduits close to a wall surface, rather than in a wall center furthest away from all such surfaces.
Most utility conduits today are therefore run through through-holes in studs. For example, in residential home construction a plumber, electrician, or communications technician will typically drill holes through the centers of wooden studs to run their pipe or cable before both sides of a wall are covered, thus hiding the utility conduits within the walls. Alternately, a crafts person may have to run utility conduits after construction.
Coincidental with our use of such hidden utility conduits has been our desire to protect them, both as and after the walls are covered. Most walls today are covered by nailing or screwing wall cover material to the studs, thus exposing the conduits passing through the studs to the risk that one of these nails or screws will damage them. Similarly, once utility conduits are “hidden” within a wall, they are at risk from anything that later penetrates the wall. Potentially, such penetration can occur anywhere in a wall and all points of a utility conduit are thus seemingly at risk. As a practical matter, however, such penetration usually is at studs and poses the greatest risk there. For example, the proud owner of a new house may want to drive a nail into a wall to hang a mirror. If this hypothetical handy-person lacks foresight, and simply drives their nail into the wall anywhere, the chances are that it will not be driven into a stud and that the mirror will not be well secured. If, per chance, the nail in this scenario encounters a utility conduit one or the other may well simply be pushed aside and the utility conduit then will not sustain critical damage. In contrast, if our handy-person is a bit more savvy about mechanics, they may seek a stud to drive their nail into, to insure that their mirror will be well secured. The handy-person may then, for instance, employ the time-honored method of thumping the wall and listening for changes in tone to determine where a stud is or they may employ an electronic stud detector. Unfortunately, if per chance the nail in this scenario is driven into a stud and there encounters a utility conduit, say, an electrical power cable, the stud will tend to hold the cable relatively fixed and this will increase the likelihood that the nail will penetrate it, potentially shorting the conductors and starting a fire.
The construction industry, regulatory authorities, and people in general have long appreciated the need to shield utility conduits at studs hidden within walls, and various approaches to this have been tried. For example, U.S. Pat. No. 4,924,646 by Marquardt; U.S. Pat. No. 3,689,681 by Searer at al.; U.S. Pat. No. 3,553,346 by Ballantyne; U.S. Pat. No. 3,297,815 Drettmann; U.S. Pat. No. 3,211,825 by Clos; and U.S. Pat. No. 3,211,824 Heiman all teach inserts usable with through-notching in studs. Basically, these inserts include a metal plate portion that protects any utility conduits running through the insert.
Another approach is taught in U.S. Pat. No. 3,240,869 by Jureit. Here a simple plate with widely spaced apart teeth is hammered onto a wooden stud. Doing this over the opening of a through-notch is all that is explicitly disclosed, but a second plate could presumably be put on the opposite side of the stud as well, and two such plates could presumably even be used on alternate sides of a stud to protect utility conduits running through a through-hole.
U.S. Pat. No. 6,642,445 by Lalancette and U.S. Pat. No. 6,061,910 by Williamson teach plates specifically for use over through-holes. These both have prongs to be driven into wooden studs, to retain the plate in place. It is the present inventor's understanding that the “stud shield” of Williamson is the most commonly used utility conduit shield in the United States today.
U.S. Pat. App. 2003/0126824 by Jensen and U.S. Pat. No. 5,595,453 by Nattel et al.; U.S. Pat. No. 5,163,254 by Zastrow et al.; and U.S. Pat. No. 4,050,205 by Ligda all teach alternate plate-based schemes for protecting utility conduits in stud through-holes. Nattel et al. and Ligda are noteworthy because they are for use with sheet metal type studs, and Zastrow et al. employs adhesive attachment to a stud surface rather than tooth, prong, or barb penetration into wooden stud material.
U.S. Pat. No. 5,079,389 by Nelson; U.S. Pat. No. 3,926,030 by Baillie; U.S. Pat. No. 3,855,413 also by Baillie; and U.S. Pat. No. 2,870,242 by Wilkerson all teach sleeves or sheaths that are inserted through a through-hole. Nelson's approach employs two hollow cylinders, with one being inserted inside the other and individual wires (the special utility conduits of concern here) then being pulled through the combination. This protects against abrasion with the through-hole of the stud as well as providing shielding. Baillie's approaches both employ a metal tube with outwardly protruding dimples. The tube is hammered into a slightly larger through-hole in a wooden stud and interference of the protruding dimples with the wooden stud material causes the tube to be retained in place. Wilkerson's approach employs one or more tubular metal sheaths that are driven into a slightly larger through-hole in a wooden stud. The sheathes are slit along their length and are desirably tapered. The act of driving the sheath or an assembly of two or more of them in concentric arrangement into a through-hole causes the diameter of the sheaths to contract. Friction against the through-hole in the wooden stud or against an outer-more sheath then holds the respective sheaths in place.
Lastly, U.S. Pat. No. 2,115,000 by Abbott teaches a sleeve or sheath approach for use with through-notching. This solution is quite elaborate and material-intensive. However, having been filed for in 1935 and issuing in 1938, this prior art reference particularly serves to illustrate how long we have considered shielding utility conduits very important and what lengths we will go to achieve this.
Unfortunately, all of the presently used approaches to shielding utility conduits have limitations or involve trade-offs. For example, as noted above, all of the approaches that are specific for use with through-notching are undesirable because through-notching undermines the strength of the studs and ultimately the walls that they are part of. Additionally, since a through-notch is inherently proximate to one side of a wall, any utility conduits passing through such through notches tend to be held proximate to that wall surface. A nail or screw that might not be long enough to reach a utility conduit in the center of a wall thus might still be long enough to reach and damage utility conduits held proximate to a wall surface. Granted, the shielding over the through-notch should help protect the conduits within it, but this still brings the rest of the conduits closer to one wall and generally exposes them to possible damage by shorter penetrations.
All of the side-of-stud plate-based approaches, both for use over through-notches and through-holes, also have another inherent limitation. They all place a hard shield proximate to a wall surface that impedes driving any nails or screws there. Of course, this is desirable if a long nail or screw would reach underlying utility conduits. But this is not necessarily always the case. For example, in the United States 2×4″ or 2×6″ studs are used in most construction, and ⅝″ wall covering may typically be used. If a 1″ through-hole is drilled in the center of a 2×4″ stud, this means, roughly, that nails or screws as long as 2″ could still even used be adjacent to the through-hole without reaching the through hole. Obviously, this possibility is totally foreclosed if a metal side-of-stud plate is used. Furthermore, side-of-stud plates inherently have some thickness and this tends to slightly further separate the wall coverings above such plates than elsewhere. This can result in a wall covering having an aesthetically unpleasing buckled or warped appearance.
Even the simplest side-of-stud plate-based approaches have a trade-off. While flat plates with projections (teeth, prongs, or barbs) are easy to make (see e.g., Williamson's stud shield, discussed above), they also require an undue quantity of material to make. Firstly, such a plate usually has to have portions extending above and below the through-notch or through-hole being covered for the projections that will be driven into a wooden stud. Secondly, even when this is not the case (see e.g., Lalancette's plate for use in limited applications and Zastrow et al's adhesive plate), side-of-stud plates need to extend more than the vertical width of the through-notch or diameter of the through-hole to protect against nails or screws driven into a stud adjacent to the plate but at an angle such that utility conduits might still be damaged. Side-of-stud plate-based approaches are also unsuitable for use after wall covering, e.g., for running new utility conduits in existing construction.
This material-intensive nature of plate-based approaches is not well appreciated in the industry, largely because it has slowly grown in importance and “conventional wisdom” is that plates are fine and their cost is simply one that must be endured. By way of example, consider that in the 1920's and 1930's each room in a typical house in the United States might have as few as one power receptacle and one light receptacle. In the late 1940's, as electrical appliances became popular, more power receptacles per room came to be used, particularly in rooms like kitchens, and wall switches for lighting also became popular. By the 1960's and 1970's every wall of appreciable size in a room usually had one or more power receptacles. This was because the consumers of home and office space tended to want it, and particularly because regulatory agencies dictated this in building codes and aggressively enforced it with permit and inspection schemes. Today this trend continues, only now for communications cable as well. The point here is that we have slowly grown to use roughly ten-fold as much utility conduit shielding as we once did, and the materials for that and their cost have become substantial.
Center-of-stud specific approaches can inherently be more materials efficient, and thus potentially more economical. Nonetheless, the multi-cylinder approach by Nelson and multi-sheath embodiments in accord with Wilkerson's approach are actually not economical with respect to the amount of material they require.
In contrast, single-sheath embodiments in accord with Wilkerson's approach are very economical with respect to material, but they have to be manufactured with awkward limitations or else used in a relatively precise manner. Wilkerson teaches that its sheaths are desirably tapered. If such taper is appreciable, the sheaths will seemingly fit in through-holes having a wide range of diameters. The problem is, however, that Wilkerson's sheaths have no mechanism other than surface friction to retain them in a through-hole, and the greater the degree of taper they have the more likely they are to simply pop back out of a through-hole. Conversely, if Wilkerson's sheaths have little taper they must be used in through-holes having a limited range of diameters. For instance picture an electrician who has just broken his or her 1″ drill bit. Using ¾″ or 1⅛″ bits will likely produce holes that will not work for 1″ Wilkerson sheaths. Furthermore, with no significant retaining mechanism, Wilkerson sheaths are not reliably useable with sheet metal type studs. [Notably, Wilkerson's filing in 1954 pre-dates the significant use of sheet metal studs and this reference does not teach the use its sheathes in such.]
Similarly, Baillie's dimpled tubes are very economical with respect to material but have other limitations. Baillie specifically teaches that its tubes must also closely fit the through-holes they are used in. Also, even though the first of the patents for this was filed for in 1973, when sheet metal studs where becoming known, Baillie does not teach and apparently it simply was not contemplated that its dimpled tubes could be used in sheet metal studs.
Accordingly, the presently most widely used utility conduit protection scheme, plates affixed to stud edges, is uneconomical and has utilitarian limitations. Similarly, all of the other known plate-based approaches suffer from at least the same problems. Conversely, present center-of-stud specific approaches are either less economical than possible, also have utilitarian limitations, or both. It therefore follows that improved utility conduit protection schemes are desirable.